As microorganisms having been practically used until now in producing polyol particularly erythritol, there are known two microorganisms i.e. Moniliella tomentosa var. pollinis CBS 461.67 and Trichosporonoides megachiliensis SN-G42 (FERM BP-1430) (which is the same as Aureobasidium sp. SN-G42 (FERM P-8940)). For the former, there are known a series of processes for producing polyol by fermentation of saccharides in industrial scale (Japanese Patent Publication Nos. 30591/1994, 30592/1994, 30593/1994 and 30594/1994). For the latter, there is known a novel microorganism having the ability to produce erythritol as well as a process for producing erythritol by fermentation with said microorganism (Japanese Patent Publication Nos. 11189/1992 and 635/1992).
For microorganisms of the genus Trichosporonoides, there is a report of Marina A. Y. Aoki in the State University of Campinas, Brazil, on conversion of glucose and sucrose into erythritol (Biotechnology Letters, Volume 15, No. 4, pp. 383-388, April 1993). According to this report, the rate of conversion of glucose into erythritol is as high as 43.0%, and the rate of conversion of sucrose into erythritol is as high as 37.4%, but the concentration of these saccharides in the culture medium is as low as 10% (W/V), so there is a problem with production in industrial scale.
Further, Ueda et al. in Mitsubishi Chemical Co., Ltd. reported that 5 strains of the genus Trichosporonoides, that is, Trichosporonoides oedocephalis CBS 649.66, Trichosporonoides madida CBS 240.79, Trichosporonoides nigrescens CBS 268.81, Trichosporonoides spathulata CBS 241.79, and Trichosporonoides megachiliensis CBS 567.85 can form erythritol from glucose (Japanese Patent Laid-Open No. 154589/1997). However, these microorganisms are not necessarily advantageous for large-scale production because the range of their culture temperatures is as narrow as 25 to 37.degree. C. (suitable temperature of 27-35.degree. C.) and a large amount of cooling water is required. Regrettably, it is known that Trichosporonoides nigrescens particularly exhibiting the best productivity of 136.0 g/L erythritol does not grow at 37.degree. C. and at a concentration of 50% glucose (infra).